Effects of precursor powder particle size on critical current density and microstructure of Bi-2223/Ag tapes

The effect of particle size distribution on the nature of the precursor powder and the subsequent phase formation and critical current density of silver sheathed Bi-3223 tapes has been studied. Three precursor powders with different particle size distributions were obtained by grinding the calcined powder for different times. The effects of precursor powder particle size were identified by a combination of XRD, SEM and EDX analysis. The results indicate that the phase formation, microstructure evolution and critical current density are sensitive to the precursor particle size distribution. It has been shown that a small particle size promotes the formation of the Bi-2223 phase, and that coarse powder leads to Ca2CuO3 and Ca2PbO4 remaining in the final tape. It has been found that too fine a powder may cause the formation of large alkaline-earth cuprate grains [(Sr,Ca)(14)Cu14O41 and (Ca,Sr)(2)CuO3]. The critical current density tends to increase when the amount and size of non-superconducting phase decrease in the final tapes. (C) 1998 Elsevier Science B.V.